Braun tube



July 5', 193 8. E. BR'L'JcHE 2,122,555

BRAUN TUBE Filed April 27, 1936 INVENTOQB ERNST BRUCHE Patented July 5, 1938 UNEED fiTA'l'ES BRAUN TUBE Ernst Briiche, Berlin-Reinickendorf, Germany,

assignor to Allgemeine Elektricitatz Gesellschaft, Berlin, Germany, a corporation of Germany Application April 27, 1936, Serial No. 76,632 In Germany April 27, 1935 3 Claims.

It has been suggested in the prior art to design the accelerator system in Braun tubes in the form of an electron-optic immersion objective comprising two cylindrical electrodes. The first one of these cylinders in this scheme is closely adjacent the cathode and it may, optionally, extend beyond it, whereas the second cylinder partly surrounds the former and extends beyond it. The second cylindrical electrode could also be replaced by an inside lining of the tube.

The potential curve on the axis of such an immersion objective is shown graphically in Fig. 1 of the drawing. The abscissa of the diagram here shown corresponds to the axis of the sys tern, while the ordinate indicates the potential U. Below the diagram is shown at the same time in schematic form the system itself comprising the cathode K and the cylinders Zl and Z2 to which suitable potentials are applied. As can be seen from the diagram, a rise of potential occurs between the cathode K and the cylinder Zl. Along Z! the shape of the potential curve is rectilinear and nearly horizontal. Between Zl and Z2 there happens another rise of potential. The lens action of the system is governed by the electrical field which arises at the said points of transition. The rectilinear shape of the potential along Zl (and also Z2) means that the potential surfaces at the said points are placed perpendicularly (or at right angles) to the axis of the system.

Now, according to this invention, in Braun tubes equipped with electrode systems of the said sort, at least the first deflection plate pair is disposed inside the first cylinder (closest to the cathode) at a point where the shape of the potential is horizontal or practically so. If the first cylinder is of sufiicient size, it will be feasible to mount also the second pair of plates inside this cylinder. However, as a general rule it will be suitable to place the second pair of plates posteriorly of the potential field producing the lens action.

The accommodation of the pair of plates inside the cylinder at greatest proximity to the cathode ofiers the advantage that the deflection of the electrons happens at points of low electron velocity, and that, moreover, the deflection systems are located as close as possible to the lens which, as will be noted, is formed at points where the first cylinder passes over to the second. The oscillographic tube thus becomes extremely sensitive.

An exemplified embodiment of the tube here disclosed is illustrated in Fig. 2. From the oathode l by the aid of the accelerative system 2, 3, an electron pattern in the form of a luminous spot is produced upon the screen 4. The cathode preferably is of the hollow type having a small and sharply bounded exit opening.

The cathode l, in order to improve the image,

is surrounded by an electrode 5 in the shape of an annular disk being kept at cathode potential. Both the cylinder 2 as well as cylinder 3 have bores through which leads and supporting means for the pairs of plates 6 and I may be passed. The plates themselves are of but reduced size, and they will thus not impair or disturb the shape of the potential seeing that the potential will be nearly constant also at the points where the plates are mounted.

I claim:

1. A cathode ray tube comprising, an envelope, an electron emitter within the envelope and positioned at one end thereof, a luminescent screen also within the envelope and positioned at the end thereof opposite the emitter, a pair of cylindrical accelerating and focussing electrodes supported within the tube in the region adjacent the emitter and each longitudinally spaced therefrom and telescopically positioned relative to each other so that one cylinder partially surrounds the other, said electrodes being adapted to have applied thereto positive potentials relative to the emitter to develop an electrostatic field to form the emitted electron stream into a sharply defined spot focussing upon the screen, and a pair of beam deflecting electrodes positioned internally of the cylindrical electrode nearest the emitter, said deflecting electrodes being located within the cylindrical electrode in a region of electrical field distribution where the shape of the potential characteristic is substantially uniform.

2. The tube claimed in claim 1 comprising in addition a second pair of beam deflecting electrodes positioned within the cylindrical electrode most remote from the emitter.

3. A cathode ray tube comprising, an envelope, an electron emitter within the envelope and positioned at one end thereof, a luminescent screen also within the envelope and positioned at the end thereof opposite the emitter, a pair of cylindrical accelerating and focussing electrodes supported within the tube in the region adjacent the emitter and each longitudinally spaced therefrom, said electrodes being adapted to have applied thereto positive potentials relative to the emitter to develop an electrostatic field to form the emitted electron stream into a sharply defined spot iocussing upon the screen, and a pair of beam deflecting electrodes positioned internally of the cylindrical electrode nearest the emitter, said deflecting electrodes being located within the cylindrical electrode in a region of electrical field distribution where the shape of the potential characteristic is substantially uniform, and a second pair of beam deflecting electrodes positioned within the cylindricalelectrode most remote from the emitter.

ERNST BRUCHE. 

